For the 2016 election cycle, the group spent just over $1 million on candidates for federal office. Congressional candidates from Florida, including Republican Sen. Marco Rubio, received the third-biggest total from NRA PACs; individual members, employees or owners; and individuals' immediate families, according to the CRP.

Only candidates from California and Texas, the nation's most populous states, received bigger totals. Florida is estimated to have the third-biggest population.

The total spent toward individual candidates compares with $3.2 million on lobbying in 2016 and some $54.4 million on outside spending. The latter category includes spending on issue-oriented campaigns that may benefit a particular candidate but isn't tied directly to the candidate's campaign.

One reason for the relatively small amount of direct spending on federal candidates may be that much of the battle over gun regulation is being fought in statehouses, not on Capitol Hill. While federal gun laws are relatively weak, the number of state regulations governing the purchase and use of firearms varies greatly.

California, with some of the strictest gun regulations in the country, had 104 provisions related to guns as of 2016, according to a state-by-state inventory by stategunlaws.org, a group that tracks gun regulations.

Idaho and Montana, with just four gun-related provisions each, had the fewest.

As for NRA campaign contributions, the overwhelming majority of that group's direct spending, roughly 90 cents on the dollar, goes to Republicans.

The biggest states, with the largest congressional delegations, tend to see the most NRA spending on candidates supporting gun rights.